1. Field of the Invention
This invention relates to a suspension strut having an increased stroke.
2. Description of the Prior Art
Telescoping struts have been used in automotive suspensions for many years. An example of such use is disclosed in U.S. Pat. No. 2,660,449, which defines the classic MacPherson strut configuration in which the lower end of the strut is rigidly attached to the wheel carrier and the upper end of the strut is pivotally attached to the body or chassis. Another type of strut suspension, the so called modified MacPherson configuration, differs from the original MacPherson design principally in that the suspension spring bears upon a lower control arm rather than being concentrically located about the strut itself. With either of these designs, the strut is subjected to beam stress caused by the weight of the vehicle acting upwardly through the spindle. This beam stress causes friction within the strut, acting at the upper bearing where the piston rod passes into the interior of the strut, and also acting upon the strut piston. The presence of this friction can cause the piston rod and piston to cock within the strut cylinder bore; avoidance of such action requires that the distance between the upper bearing and the piston be not less than a predetermined minimum value when the suspension system is in full rebound condition--i.e. when the wheel has traveled vertically the maximum distance away from vehicle's chassis or body in a downward direction.
The distance between the upper rod bearing and the piston in the full rebound position is termed "bearing span". It is the purpose of present invention to maintain bearing span distance while allowing a reduction in the overall length of the strut. This is accomplished by means of a telescoping plunger and lower bearing arrangement mounted to the strut piston rod.
U.S. Pat. No. 1,150,925 discloses a dash pot for an adding machine having a telescoping plunger carried within the piston. U.S. Pat. No. 2,379,750 discloses a hydraulic shock absorber having a shut-off valve attached to a plunger telescopingly mounted into the shock absorber piston rod. U.S. Pat. No. 2,575,389 discloses a single unit hydraulic check for a garment pressing machine having part of its valving mechanism projecting upwardly from the foot of the check unit into a receiving bore within the check's piston. Finally, U.S. Pat. No. 3,036,669 discloses a hydraulic shock absorber with compression cut-off, including an auxiliary piston which cooperates with a secondary cylinder to produce additional resistance to movement of the shock absorber at its final stages of compression.